Thiourea Mitigates Potassium Deficiency in Soybean Varieties Through Redox or ABA Dependent Mechanisms

The potassium (K) fertilizer resource is limited worldwide and hence, there is a need to increase potassium-use efficiency. In view of this, the present study investigated the efficacy of thiourea (TU; a non-physiological thiol) for ameliorating the K-deficiency (KD) in soybean varieties. The expression pattern of 19 K + -transporters revealed Maus47 (MS), as transcriptionally more responsive than Gujosoya2 (GS) variety, under KD conditions. Based on the photosynthetic efficiency, MS was found to be more tolerant relative to GS under KD conditions. Upon TU supplementation, significant amelioration in phenotype was observed under KD treatment, without any significant change in K-accumulation, except for 2.99-fold increase in roots of MS-variety under KD + TU treatment when compared to KD treatment. This coincided with upregulated expression of GmAKT2/3 (1.39-fold) and increased activities of enzymatic antioxidants, which suggested “KD-avoidance” in MS-variety was redox-dependent. ABA levels were increased (1.60-fold) and decreased (0.87-fold) in GS and MS varieties, respectively under KD + TU treatment compared with those of KD treatment. Additionally, the preferential upregulation of ABA biosynthesis/signaling genes was observed in GS (median: 0.17) than in MS (median: − 1.22) variety, suggesting that TU induced “KD-tolerance” in GS-variety was ABA-dependent. Thus, our findings gives the physiological and molecular basis for TU-mediated amelioration of KD-induced symptoms in soybean.